[RISCV] Rematerialize vmv.v.x (#107993)

Even though vmv.v.x has a non constant scalar operand, we can still
rematerialize it because we have split register allocation between
vectors and scalars.

InlineSpiller will check to make sure that the scalar operand is live at
the point where the rematerialization occurs, so this won't extend any
scalar live ranges. However this also means we may not be able to
rematerialize in some cases, as shown in @vmv.v.x_needs_extended.

It might be worthwhile teaching InlineSpiller to extend scalar live
ranges in a future patch. I experimented with this locally and it
reduced spills on 531.deepsjeng_r by a further 3%.

Author: lukel97

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -169,6 +169,7 @@ Register RISCVInstrInfo::isStoreToStackSlot(const MachineInstr &MI,
 bool RISCVInstrInfo::isReallyTriviallyReMaterializable(
     const MachineInstr &MI) const {
   switch (RISCV::getRVVMCOpcode(MI.getOpcode())) {
+  case RISCV::VMV_V_X:
   case RISCV::VMV_V_I:
   case RISCV::VID_V:
     if (MI.getOperand(1).isUndef() &&

llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td

@@ -2475,6 +2475,7 @@ multiclass VPseudoUnaryVMV_V_X_I {
         def "_V_" # mx : VPseudoUnaryNoMask<m.vrclass, m.vrclass>,
                          SchedUnary<"WriteVIMovV", "ReadVIMovV", mx,
                                     forcePassthruRead=true>;
+        let isReMaterializable = 1 in
         def "_X_" # mx : VPseudoUnaryNoMask<m.vrclass, GPR>,
                          SchedUnary<"WriteVIMovX", "ReadVIMovX", mx,
                                     forcePassthruRead=true>;

llvm/test/CodeGen/RISCV/rvv/ctpop-vp.ll

@@ -2022,14 +2022,9 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64(<vscale x 16 x i64> %va, <vscale x
 ; RV32-NEXT:    mul a1, a1, a2
 ; RV32-NEXT:    sub sp, sp, a1
 ; RV32-NEXT:    .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x38, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 56 * vlenb
-; RV32-NEXT:    vmv1r.v v24, v0
+; RV32-NEXT:    vmv1r.v v7, v0
 ; RV32-NEXT:    csrr a1, vlenb
-; RV32-NEXT:    slli a1, a1, 5
-; RV32-NEXT:    add a1, sp, a1
-; RV32-NEXT:    addi a1, a1, 16
-; RV32-NEXT:    vs8r.v v16, (a1) # Unknown-size Folded Spill
-; RV32-NEXT:    csrr a1, vlenb
-; RV32-NEXT:    li a2, 48
+; RV32-NEXT:    li a2, 40
 ; RV32-NEXT:    mul a1, a1, a2
 ; RV32-NEXT:    add a1, sp, a1
 ; RV32-NEXT:    addi a1, a1, 16
@@ -2045,101 +2040,88 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64(<vscale x 16 x i64> %va, <vscale x
 ; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
 ; RV32-NEXT:    vsrl.vi v8, v16, 1, v0.t
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    li a4, 40
+; RV32-NEXT:    li a4, 48
 ; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
 ; RV32-NEXT:    vs8r.v v8, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    lui a3, 349525
 ; RV32-NEXT:    addi a3, a3, 1365
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
-; RV32-NEXT:    vmv.v.x v16, a3
-; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    li a4, 24
-; RV32-NEXT:    mul a3, a3, a4
-; RV32-NEXT:    add a3, sp, a3
-; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vs8r.v v16, (a3) # Unknown-size Folded Spill
+; RV32-NEXT:    vmv.v.x v8, a3
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    li a4, 40
-; RV32-NEXT:    mul a3, a3, a4
+; RV32-NEXT:    slli a3, a3, 5
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vl8r.v v8, (a3) # Unknown-size Folded Reload
-; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
-; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
+; RV32-NEXT:    vs8r.v v8, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    csrr a3, vlenb
 ; RV32-NEXT:    slli a3, a3, 5
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vl8r.v v16, (a3) # Unknown-size Folded Reload
-; RV32-NEXT:    vsub.vv v8, v16, v8, v0.t
+; RV32-NEXT:    vl8r.v v8, (a3) # Unknown-size Folded Reload
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 5
+; RV32-NEXT:    li a4, 48
+; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vs8r.v v8, (a3) # Unknown-size Folded Spill
+; RV32-NEXT:    vl8r.v v24, (a3) # Unknown-size Folded Reload
+; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
+; RV32-NEXT:    vand.vv v8, v24, v8, v0.t
+; RV32-NEXT:    vsub.vv v16, v16, v8, v0.t
 ; RV32-NEXT:    lui a3, 209715
 ; RV32-NEXT:    addi a3, a3, 819
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
-; RV32-NEXT:    vmv.v.x v16, a3
-; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 5
-; RV32-NEXT:    add a3, sp, a3
-; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vl8r.v v8, (a3) # Unknown-size Folded Reload
-; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
-; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
+; RV32-NEXT:    vmv.v.x v8, a3
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 4
+; RV32-NEXT:    li a4, 48
+; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
 ; RV32-NEXT:    vs8r.v v8, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 5
+; RV32-NEXT:    li a4, 48
+; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
 ; RV32-NEXT:    vl8r.v v8, (a3) # Unknown-size Folded Reload
-; RV32-NEXT:    vsrl.vi v8, v8, 2, v0.t
+; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
+; RV32-NEXT:    vand.vv v8, v16, v8, v0.t
+; RV32-NEXT:    vsrl.vi v16, v16, 2, v0.t
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    li a4, 40
+; RV32-NEXT:    li a4, 48
 ; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vs8r.v v16, (a3) # Unknown-size Folded Spill
-; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
-; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 4
-; RV32-NEXT:    add a3, sp, a3
-; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vl8r.v v16, (a3) # Unknown-size Folded Reload
-; RV32-NEXT:    vadd.vv v8, v16, v8, v0.t
+; RV32-NEXT:    vl8r.v v24, (a3) # Unknown-size Folded Reload
+; RV32-NEXT:    vand.vv v16, v16, v24, v0.t
+; RV32-NEXT:    vadd.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    vsrl.vi v16, v8, 4, v0.t
 ; RV32-NEXT:    vadd.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    lui a3, 61681
 ; RV32-NEXT:    addi a3, a3, -241
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
 ; RV32-NEXT:    vmv.v.x v16, a3
 ; RV32-NEXT:    csrr a3, vlenb
-; RV32-NEXT:    slli a3, a3, 5
+; RV32-NEXT:    li a4, 24
+; RV32-NEXT:    mul a3, a3, a4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
 ; RV32-NEXT:    vs8r.v v16, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
-; RV32-NEXT:    vand.vv v16, v8, v16, v0.t
+; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    lui a3, 4112
 ; RV32-NEXT:    addi a3, a3, 257
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
-; RV32-NEXT:    vmv.v.x v8, a3
+; RV32-NEXT:    vmv.v.x v16, a3
 ; RV32-NEXT:    csrr a3, vlenb
 ; RV32-NEXT:    slli a3, a3, 4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
-; RV32-NEXT:    vs8r.v v8, (a3) # Unknown-size Folded Spill
+; RV32-NEXT:    vs8r.v v16, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
-; RV32-NEXT:    vmul.vv v16, v16, v8, v0.t
+; RV32-NEXT:    vmul.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    li a2, 56
-; RV32-NEXT:    vsrl.vx v8, v16, a2, v0.t
+; RV32-NEXT:    vsrl.vx v8, v8, a2, v0.t
 ; RV32-NEXT:    csrr a3, vlenb
 ; RV32-NEXT:    slli a3, a3, 3
 ; RV32-NEXT:    add a3, sp, a3
@@ -2149,8 +2131,8 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64(<vscale x 16 x i64> %va, <vscale x
 ; RV32-NEXT:  # %bb.1:
 ; RV32-NEXT:    mv a0, a1
 ; RV32-NEXT:  .LBB46_2:
-; RV32-NEXT:    vmv1r.v v0, v24
-; RV32-NEXT:    li a3, 48
+; RV32-NEXT:    vmv1r.v v0, v7
+; RV32-NEXT:    li a3, 40
 ; RV32-NEXT:    mul a1, a1, a3
 ; RV32-NEXT:    add a1, sp, a1
 ; RV32-NEXT:    addi a1, a1, 16
@@ -2160,71 +2142,64 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64(<vscale x 16 x i64> %va, <vscale x
 ; RV32-NEXT:    addi a0, sp, 16
 ; RV32-NEXT:    vs8r.v v8, (a0) # Unknown-size Folded Spill
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 24
-; RV32-NEXT:    mul a0, a0, a1
-; RV32-NEXT:    add a0, sp, a0
-; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    addi a0, sp, 16
-; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vand.vv v16, v8, v16, v0.t
-; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 48
-; RV32-NEXT:    mul a0, a0, a1
+; RV32-NEXT:    slli a0, a0, 5
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vsub.vv v8, v8, v16, v0.t
+; RV32-NEXT:    addi a0, sp, 16
+; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
+; RV32-NEXT:    vand.vv v8, v16, v8, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 48
+; RV32-NEXT:    li a1, 40
 ; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vs8r.v v8, (a0) # Unknown-size Folded Spill
+; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
+; RV32-NEXT:    vsub.vv v8, v16, v8, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
 ; RV32-NEXT:    li a1, 40
 ; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
+; RV32-NEXT:    vs8r.v v8, (a0) # Unknown-size Folded Spill
 ; RV32-NEXT:    csrr a0, vlenb
 ; RV32-NEXT:    li a1, 48
 ; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 24
+; RV32-NEXT:    li a1, 40
 ; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vs8r.v v8, (a0) # Unknown-size Folded Spill
+; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
+; RV32-NEXT:    vand.vv v16, v16, v8, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 48
-; RV32-NEXT:    mul a0, a0, a1
+; RV32-NEXT:    slli a0, a0, 5
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vsrl.vi v16, v8, 2, v0.t
+; RV32-NEXT:    vs8r.v v16, (a0) # Unknown-size Folded Spill
+; RV32-NEXT:    vmv8r.v v16, v8
 ; RV32-NEXT:    csrr a0, vlenb
 ; RV32-NEXT:    li a1, 40
 ; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vand.vv v16, v16, v8, v0.t
+; RV32-NEXT:    vsrl.vi v8, v8, 2, v0.t
+; RV32-NEXT:    vand.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    li a1, 24
-; RV32-NEXT:    mul a0, a0, a1
+; RV32-NEXT:    slli a0, a0, 5
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
-; RV32-NEXT:    vl8r.v v8, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vadd.vv v8, v8, v16, v0.t
+; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
+; RV32-NEXT:    vadd.vv v8, v16, v8, v0.t
 ; RV32-NEXT:    vsrl.vi v16, v8, 4, v0.t
 ; RV32-NEXT:    vadd.vv v8, v8, v16, v0.t
 ; RV32-NEXT:    csrr a0, vlenb
-; RV32-NEXT:    slli a0, a0, 5
+; RV32-NEXT:    li a1, 24
+; RV32-NEXT:    mul a0, a0, a1
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v16, (a0) # Unknown-size Folded Reload
@@ -2386,23 +2361,23 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64_unmasked(<vscale x 16 x i64> %va,
 ; RV32-NEXT:    vs8r.v v0, (a3) # Unknown-size Folded Spill
 ; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
 ; RV32-NEXT:    vand.vv v24, v24, v0
-; RV32-NEXT:    vsub.vv v24, v16, v24
+; RV32-NEXT:    vsub.vv v16, v16, v24
 ; RV32-NEXT:    lui a3, 209715
 ; RV32-NEXT:    addi a3, a3, 819
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
 ; RV32-NEXT:    vmv.v.x v0, a3
 ; RV32-NEXT:    vsetvli zero, a2, e64, m8, ta, ma
-; RV32-NEXT:    vand.vv v16, v24, v0
-; RV32-NEXT:    vsrl.vi v24, v24, 2
+; RV32-NEXT:    vand.vv v24, v16, v0
+; RV32-NEXT:    vsrl.vi v16, v16, 2
 ; RV32-NEXT:    csrr a3, vlenb
 ; RV32-NEXT:    slli a3, a3, 4
 ; RV32-NEXT:    add a3, sp, a3
 ; RV32-NEXT:    addi a3, a3, 16
 ; RV32-NEXT:    vs8r.v v0, (a3) # Unknown-size Folded Spill
-; RV32-NEXT:    vand.vv v24, v24, v0
-; RV32-NEXT:    vadd.vv v24, v16, v24
-; RV32-NEXT:    vsrl.vi v16, v24, 4
+; RV32-NEXT:    vand.vv v16, v16, v0
 ; RV32-NEXT:    vadd.vv v16, v24, v16
+; RV32-NEXT:    vsrl.vi v24, v16, 4
+; RV32-NEXT:    vadd.vv v16, v16, v24
 ; RV32-NEXT:    lui a3, 61681
 ; RV32-NEXT:    addi a3, a3, -241
 ; RV32-NEXT:    vsetvli a4, zero, e32, m8, ta, ma
@@ -2437,16 +2412,16 @@ define <vscale x 16 x i64> @vp_ctpop_nxv16i64_unmasked(<vscale x 16 x i64> %va,
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v0, (a0) # Unknown-size Folded Reload
 ; RV32-NEXT:    vand.vv v24, v24, v0
-; RV32-NEXT:    vsub.vv v24, v8, v24
+; RV32-NEXT:    vsub.vv v8, v8, v24
 ; RV32-NEXT:    csrr a0, vlenb
 ; RV32-NEXT:    slli a0, a0, 4
 ; RV32-NEXT:    add a0, sp, a0
 ; RV32-NEXT:    addi a0, a0, 16
 ; RV32-NEXT:    vl8r.v v0, (a0) # Unknown-size Folded Reload
-; RV32-NEXT:    vand.vv v8, v24, v0
-; RV32-NEXT:    vsrl.vi v24, v24, 2
-; RV32-NEXT:    vand.vv v24, v24, v0
-; RV32-NEXT:    vadd.vv v8, v8, v24
+; RV32-NEXT:    vand.vv v24, v8, v0
+; RV32-NEXT:    vsrl.vi v8, v8, 2
+; RV32-NEXT:    vand.vv v8, v8, v0
+; RV32-NEXT:    vadd.vv v8, v24, v8
 ; RV32-NEXT:    vsrl.vi v24, v8, 4
 ; RV32-NEXT:    vadd.vv v8, v8, v24
 ; RV32-NEXT:    csrr a0, vlenb